1. Field of the Invention
The present invention relates to a drum-in disc brake in which a drum brake is incorporated in a central portion of a disc rotor of a disc brake. More particularly, the present invention concerns improvements for realizing the reduction of fabrication steps and assembling steps and the improvement of the detachability and attachability of the disc rotor during maintenance and the like.
2. Description of the Related Art
FIGS. 8 and 9 show a conventional example of a drum-in disc brake.
A drum-in disc brake 1 shown here is disclosed in JP-A-2-66330, and is constructed such that a drum brake 23 is incorporated in a central portion of a disc rotor 3 of a disc brake 15.
To give a more detailed description, the disc brake 15 is used as a service brake and includes: the disc rotor 3 which is mounted on the wheel side and is formed by integrating a cylindrical drum portion 3a having a bottom and a rotor portion 3b jutting out in the form of a collar from an edge of an opening of the drum portion 3a toward the radially outward side; a caliper 9 for supporting a pair of friction pads 5 and 6 disposed in face-to-face relation with the rotor portion 3b placed therebetween in such a manner as to be capable of pressing the pair of friction pads 5 and 6 against the rotor portion 3b; and a support member 13 which is fixedly fitted on the vehicle body side and supports the caliper 9 in such a manner as to be capable of displacing the caliper 9 in the axial direction of the disc rotor 3 (in the direction of arrow (A) in FIG. 9) by a pair of caliper slide pins 11 extending in the axial direction of the disc rotor 3.
Meanwhile, the drum brake 23 is used as a parking brake and includes a backing plate 17 mounted on the vehicle body side so as to cover the opening of the drum portion 3a, and a pair of brake shoes 19 and 20 which are supported by the backing plate 17 and are capable of pressing against the inner peripheral surface of the drum portion 3a. 
With the conventional drum-in disc brake 1, however, as shown in the drawings, the support member 13 of the disc brake 15 and the backing plate 17 of the drum brake 23 are formed separately, and are arranged to be integrated by fastening with screws or the like after being fabricated individually. Therefore, there has been a problem in that the numbers of fabrication steps and assembling steps increase, leading to an increase in the manufacturing cost.
In addition, since the arrangement provided is such that, as shown in the drawings, the positions where the caliper slide pins 11 are provided are set on a circumference located inwardly of the outside diameter of the rotor portion 3b, and the caliper slide pins 11 are present only on one side of the disc rotor 3, there has been a possibility that a bending stress can be applied to the caliper 9 due to the braking torque of the outer-side friction pad 6 located away from the caliper slide pins 11 during the application of the service brake. This may lead to an increase in the sliding resistance due to the caliper slide pins 11 and the uneven wear of the friction pads.
Further, to pull out the disc rotor 3 in the axial direction for the purpose of the maintenance of the-brake, it is necessary to remove first the two caliper slide pins 11 located in the range smaller than the outside diameter of the disc rotor and then to remove the caliper 9, so that the maintenance operation of the disc rotor has not been easy.
The present invention has been devised in view of the above-described circumstances, and its object is to provide a drum-in disc brake which is capable of realizing the reduction of fabrication steps and assembling steps and the improvement of the detachability and attachability of the disc rotor during maintenance and the like.
To attain the above-object of the present invention, there is provided a drum-in disc brake for braking a rotating member which is rotatable with a wheel and formed by integrating a cylindrical drum portion and a rotor portion jutting out in the form of a collar from the drum portion toward a radially outward side. The drum-in disc includes a disc brake and a drum brake. The disc brake includes: an inner friction pad and an outer friction pad, respectively disposed in face-to-face relation with the rotor portion placed therebetween; a caliper for pressing the inner friction pad and the outer friction pad against the rotor portion; and a support member which is fixedly fitted on a vehicle body side and supports the caliper, wherein the support member is capable of displacing the caliper in an axial direction of the rotating member by caliper slide pins. The drum brake includes: a backing plate mounted on the vehicle body side; and brake shoes which are respectively supported by the backing plate and are capable of pressing against an inner peripheral surface of the drum portion. The drum-in disc brake is capable of effecting braking by the disc brake and braking by the drum brake, the support member of the disc brake and the backing plate of the drum brake are formed integrally, and the disc brake is constructed such that the outer friction pad is supported by a claw portion of the caliper so that the brake torque of the outer friction pad is transmitted to the support member through the caliper and the caliper slide pins, and pin supporting portions for respectively supporting the caliper slide pins are provided in the support member so that the caliper slide pins supporting the caliper are passed through on a radially outward side of the rotor portion.
In accordance with the above-described arrangement, the support member and the backing plate are integrally formed to reduce the number of constituent parts. Further, as compared with the case where the support member and the backing plate are formed as separate parts, it is possible to reduce the quantity of screw members and the like necessary for fixation to the vehicle body. Thus, by the reduction of the numbers of fabrication steps and assembling steps, it is possible to attain the reduction of the manufacturing cost.
In addition, since the structure provided is such that the caliper slide pins straddle an outer periphery of the disc rotor, and the caliper can be supported-uniformly on both sides of the rotor portion, it becomes difficult for an inclination or the like to occur in the caliper due to the braking torque of the friction pads during the application of a service brake, and it is possible to suppress an increase in the frictional resistance based on the caliper slide pins and reduce the uneven wear of the friction pads.
Furthermore, since the pin supporting portions are passed through on the outer side of the outside diameter of the rotor portion, when the disc rotor is pulled out in the axial direction for the purpose of such as the maintenance of the brake, if only one caliper slide pin is removed, and the caliper is rotated about the remaining caliper slide pin, there is no longer an obstacle in the axial direction of the disc rotor. Hence, even if the caliper is not removed, it is possible to pull out the disc rotor. Accordingly, it is possible to realize the improvement of the detachability and attachability of the disc rotor during maintenance and the like.
It should be noted that, in the above-described drum-in disc brake, it is preferred that the support member and the backing plate are integrally molded by casting an aluminum material. By so doing, it is possible to attain light weight at the same time.